JPH04233948A - Mechanical working for converting pvc-containing noncompatible polymer mixture into plastic compound product - Google Patents

Abstract

The invention relates to the flow enhancement of PVC-containing compositions, such as PVC/ABS polymer mixtures, to be impact-modified, during their processing, for example during injection moulding, on processing machines by means of alkyl methacrylate-based polymers built up using at least 50% by weight of methyl methacrylate and from 2 to 50% by weight of C2-C8-alkyl methacrylates as monomers and having molecular weights @w in the range from 2,000 to </= 20,000 g/mol.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention uses alkyl methacrylate-based polymers to reduce PVC on processing machines.
- Concerning flow improvement when processing contained materials.

0002

BACKGROUND OF THE INVENTION Whereas flexible PVC has long been an easily processable plastic due to its plasticizer content, thermoplastic processing of pure high-molecular-weight PVC requires, in particular, There were significant obstacles in terms of thermal instability and rheological behavior of molecular weight PVC. These obstacles can be overcome by the addition of various auxiliaries, so that the P to be processed
VC always consists of one mixture of various components. A major challenge for lubricants used as processing aids with other additives is the high viscosity of PV in various processing machines.
C-Improving the flow of the high viscosity PVC melt during deformation and plasticization of the melt. The lubricant reduces the frictional resistance of the PVC-particles in the melt, thereby preventing the generation of significant frictional heat, and thus also making the frictional resistance between the surface of the processing machine and the melt as small as possible. Prevent high polymer temperatures. As a result, PVC decomposition reactions which may be caused by shear forces and overheating due to mechanical damage are avoided or significantly reduced. For the processing of rigid PVC into semi-finished and finished products, polymeric processing aids such as polymethyl methacrylate (PMMA), which have a shortening of the plasticization process and, among other things, an improvement of the rheological properties in the thermoplastic state ) is used as the basis for 2-300 to almost 103 g/
Unlike other additives that influence the rheology, such as the already mentioned plasticizers and lubricants, which have a molecular weight in molar, the molecular weight of polymeric processing aids based on PMMA M
w (weight average) is 1.2 x 105 to 2.5 x 106
g/mol (Kunststoff-Hand
buch 2/1, Polyvinyl chlori
d, 2nd edition, 1986, Carl Hanser
Verlag, Muenchen, Vienna, 595~
597 pages).

Federal Republic of Germany Patent Application No. 3542
From the description in No. 469, styrene, α-methylstyrene, p-methylstyrene, vinyltoluol,
consisting of (meth)acrylonitrile, methyl methacrylate or mixtures of these substances, with a limiting viscosity of 2 to 15 ml/g (measured in dimethylformamide at 25°C)
and moldings based on vinyl chloride polymers whose overall properties, especially those of processability, can be clearly improved by the addition of thermoplastic polymers with a sulfur content of 1.15 to 3.95% by weight. The materials are known.

PVC can be converted to modified PVC by mixing another thermoplastic resin with an elastomer, provided that:
Mixtures, so-called formulations, with industrially valuable properties are obtained, for example PVC plastics with high impact strength or improved heat resistance. Structural engineering materials for the production of casings, for example PVS/
ABS-compound, in which case the impact resistance of PVC is
The incorporation of ABS-rubber provides a substantial improvement. PVC and ABS are two incompatible polymers, ie, a mixture of the two polymers is two-phase. PVC
- In the case of machining of ABS mixtures, for example in the case of injection molding of large parts, the incompatibility of the two polymers can lead to a high rejection rate of the processed polymer formulations. Macroscopically non-uniform regions appear. This non-uniformity can be seen in the processed parts as striations, flaking, flaking, and splitting into different color areas. This non-uniformity of the injection molded part results from non-uniformities in the flow of the molten mixture through the processing machine.

[0005]

Therefore, mixtures of PVC and other thermoplastically processable polymers, such as mechanically incompatible formulations such as, for example, PVC/ABS blends, are therefore difficult to solve. The task was to prepare a PVC/ABS mixture to be processed into objects and to ensure that, during processing of this mixture, finished parts were obtained without areas of macroscopic inhomogeneities.

[0006]

[Means for solving the problem] By using a polymer based on alkyl methacrylate, which is a copolymer of methyl methacrylate and has a molecular weight Mw (weight average) in the range from 2,000 to ≦20,000, Plastics to correspond to PVC-containing polymer mixtures of
It has been found that mechanical processing of the blend-product can be carried out reliably without areas of macroscopic inhomogeneity.

The invention comprises adding to the polymer mixture for mechanical processing a C1-C8-alkyl methacrylate copolymer having a molecular weight Mw (weight average) in g/mol in the range from 2000 to ≦20000. A process for the mechanical processing of incompatible PVC-containing polymer mixtures into plastic compound products, characterized in that

The rheology modifier according to the invention is based on alkyl methacrylate polymers.
The molecular weight Mw (weight average) of
~10,000. Flow improvers (Flies)
This rheological modifier, also called sverbesserer, contains 50-98% by weight of methyl methacrylate;
Methyl methacrylate consisting of 2 to 50% by weight of an alkyl methacrylic ester having 2 to 8 carbon atoms in the alkyl group and 0 to 48% by weight of another copolymer.
It is a copolymer. The processing according to the invention of the polymer mixture is preferably carried out on an injection molding machine and in particular on PVC-AB
The proportion of ABS is 30 to 70% by weight relative to the total proportion of S.
It makes sense to process PVC/ABS mixtures into PVC formulations with improved impact resistance, which are used, for example, as chassis parts, for example for computer casings.

The results of the present invention are surprising. rigid PV
When thermoplastically processing C into semi-finished and finished products,
Based on polymethyl methacrylate, 1.2 x 105
Polymeric processing aids with a molecular weight of ~2.5 x 106, such as Irgamod® from Ciba Geigy, improve rheological properties and provide improved mechanical properties in the thermoplastic state. On the other hand, such additives are suitable for PVC mixtures containing impact modifiers, e.g.
The thermoplastic processing of VC-ABS mixtures has a disadvantageous effect due to uncontrollable effects with a high reject rate. Various of such PMMA-types with Mw (weight average) >50 000 g/mol as well as commercial polymers based on functional groups and such polymers with a molecular weight of 375 000 g/mol or PVA-PE (70/30). Coalescing plasticizers (provided that the injection-molded parts have a tendency to adhesion and adhesion formation due to the high proportion of plasticizers) are added during the thermoplastic processing of the polymer mixture, e.g. during injection molding. Either the rheological properties of the polymer mixture could not be improved or the molded parts exhibited other drawbacks. The addition of C1-C8-alkyl methacrylate copolymers of significantly lower molecular weight in the first place led to a surprising solution to the problem. According to the state of the art, the present invention provides such an injection molded part that the heat deformation resistance of the injection molded part and, above all, the level of its impact strength are uniformly produced and are not reduced by the additives according to the invention. The invention was not something that could be easily deduced.

0010

[Action] Incompatible PVC, especially with improved impact resistance
- The method according to the invention for the mechanical production of formulations comprises:
PVC-types of various production methods, e.g. suspension-PVC,
It is carried out using emulsion-PVC or bulk-PVC. In order to ensure a good thorough mixing of the PVC with the polymers and processing aids to be incorporated, the PVC is preferably used in powdered or granular form with a particle size of 1 to 2 mm. The use of spray-dried products derived from emulsion polymers is advantageous.

Industrially important PV with improved impact resistance
For the preparation of C-polymer mixtures, in particular they can be prepared in various ways (Ullmanns, Encyk).
technique
n Chemie, 4th edition, Volume 19, 277-28
Of particular importance are the ABS polymers used for the production of mixtures to be mechanically processed, such as the finely divided PVC components (see page 7) and the finely divided PVC components.

[0012] The PVC and ABS polymers have a weight ratio of 70:
30-30:70, preferably weight ratio 60:40-40:6
0, preferably in a weight ratio of about 50:50, is used according to the invention for the production of molded parts with improved impact resistance.

The low-molecular weight C1-C8-alkyl methacrylate copolymer additive according to the invention has been tested on the basis of various tests and during the processing of the finely divided mixture into the products obtained during these tests. Acts as a flow improver. Relatively low-molecular polyalkyl methacrylates with a molecular weight in the range from 2000 to 20000 g/mol are composed of methacrylic acid alkyl esters having 1 to 8 C atoms in the alkyl group, optionally further monomers, especially alkyl Even in the presence of an acrylic acid alkyl ester having 1 to 8 C atoms in the group, it is polymerized by a known conventional method,
However, at least 50% by weight of methacrylic acid methyl ester is used as the main monomer (Rauch-P
untigam, Voelker, Acryl-und
Methacrylverbindungen, S
pringer Verlag Berlin, H
Eidelberg, New York, 1967)
. The polymerization is carried out as bulk, suspension or emulsion polymerization. The additives according to the invention are preferably produced by emulsion polymerization and obtained from the emulsion by spray drying. In this case, the additives are of a particle size that is suitable for mixing. Polymers of bulk and suspension polymerization must be mechanically comminuted to still give the optimum additive form.

According to the invention, the degree of polymerization of the processing aid and the molecular weight determined together with this degree of polymerization can be adjusted by known methods (
Rauch Puntigam, Voelker, supra cit.), for example by adjusting the ratio of initiator to monomer or adding regulators as chain transfer agents. As known chain transfer agents, for example aliphatic chlorohydrocarbons or preferably aliphatic mercaptans are used. Useful mercaptans are, for example, n-butyl mercaptan, n-dodecyl mercaptan, tert. -dodecylmercaptan, thioglycolic acid-2-ethylhexyl ester. With a molecular weight Mw of 2000-20 000 g/mol determined by gel permeation chromatography, the processing aid according to the invention has a molecular weight Mw of 3-20 ml/g determined in chloroform as solvent according to DIN 51562.
solution viscosity (in the range 5 to 10 ml/g)
ηsp/c). On the contrary, high molecular weight PVs based on polymethacrylates according to the state of the art
The C-additive has a solution viscosity in chloroform (η sp/c) of 50-500 ml/g, which is 1.2 x 1
This corresponds to a molecular weight Mw of 0.05 to 2.5×10 6 g/mol. The known high molecular weight PVC additives mentioned above have no influence on the effect according to the invention, as explained in detail.

The alkyl methacrylate copolymer additives according to the invention contain carbon atoms in the alkyl groups as monomers.
Methacrylic acid alkyl esters having 1 to 8 atoms 5
0 to 100% by weight, provided that at least 50% to 98% by weight of methyl methacrylate is incorporated in the polymer. 2 to 50% by weight of alkyl methacrylates having 2 to 8 C atoms in the alkyl group, together with 0 to 48% by weight of alkyl acrylates having 1 to 8 C atoms in the alkyl group, such as methyl acrylate. , acrylic acid ethyl ester, acrylic acid-
n-butyl esters may be incorporated into flow improvers according to the invention.

Accordingly, in addition to methacrylic acid methyl ester, methacrylic acid-C2-C8-alkyl esters such as methacrylic acid ethyl ester, methacrylic acid-n-propyl ester, methacrylic acid-n-butyl ester, methacrylic acid-isobutyl ester , methacrylic acid-n-hexyl ester, methacrylic acid-2
Ethylhexyl ester is used as a comonomer in the preparation of alkyl methacrylate copolymers, which are composed of at least 50% by weight of methyl methacrylate as monomer. 0-48% by weight, especially 0-20%
In an amount by weight, this polymer may also be constituted with other monomers, such as styrene or acrylonitrile.

As advantageously acting flow improvers according to the invention, the copolymers are within the molecular weight range according to the invention, consisting as monomers of 60-95% by weight of methyl methacrylate and 40-5% by weight of n-butyl methacrylate. It has been found. Hereby, examples of polymers that act as flow improvers according to the present invention have a molecular weight of 5,000 to 700
Such a heavy weight compound has a molecular weight Mw (weight average) of 0 g/mol and is composed of a monomer mixture of 80% by weight of methyl methacrylate and 20% by weight of n-butyl methacrylate or 90% by weight of methyl methacrylate and 10% by weight of n-butyl methacrylate. Chemie
Labor Betrieb 31 (1980
) pp. 232-236).

The polymeric processing aids of the invention are present in an amount of 0.1 to 10 parts by weight per 100 parts by weight, preferably in an amount of 0.5 to 8 parts by weight, especially in an amount of 1 to 5 parts by weight, It is added to the polymer mixture to be mechanically processed, for example by injection molding.

According to the invention, further additives, such as stabilizers, antioxidants, pigments, lubricants, dyes, can optionally be added to the vinyl chloride polymer material to be processed. Additives of this type are evident from the described compositions of the examples.

Evaluation method of the method according to the invention (Kunsts
toff-Handbuch 2/1, supra, 590
-594 pages).

To evaluate the flow behavior of the molding composition plasticized according to the invention, measurements were carried out in a high-pressure capillary viscometer. In this case, at a constant temperature and predetermined pressure, for example 180°C and 5 kp, in the example 18
0/5, the melt viscosity of the mixture ηs using the dimension [Pa·s], the flow rate FZ of this mixture in seconds using seconds [s] and the expansion of the strands in % B
was measured using [%]. Furthermore, in this apparatus, the melt index and MFI were measured using the dimension [g/10 minutes].

In practice, for technical evaluation of practical application, a spiral flow was ejected from the material to be tested with constant mechanical parameters, and the length of the spiral, X, was measured in [cm]. , the channel extension in [%] was calculated compared to the material without rheological modifier according to the invention.

The addition according to the invention of, for example, 3 parts of the polymethacrylate according to the invention to 100 parts of the PVC-ABS mixture increases the length of the flow helix by about 20% compared to the process unmodified according to the invention. cause an increase.

The test results are clear from the experimental "parts" table.

[0025]

[Example] “Part” based on experiment Example A. Preparation of additives according to the invention 1. Methyl methacrylate-n-butyl methacrylate 80/20-copolymer One 7l with reflux condenser, stirrer and injection vessel
In a reaction vessel, C15-paraffin sulfonate-N
a- 0.9 g of salt and 11.1 g of sodium persulfate at 20℃
was dissolved in 1200 g of demineralized water. In this solution,
While stirring at 80° C., an emulsion consisting of the following components was fed: Methyl methacrylate
2400g butyl methacrylate
600g 2-ethylhexylthioglycolate 210g
C15-paraffin sulfonate-Na-salt
27g demineralized water
The feeding time of 2053g is 4 hours.

After pouring, the batch was cooled to room temperature. In this case, 2.3 g of 1,4 diisopropylbenzole monohydrogen peroxide and 1.8 g of sodium hydroxymethylsulfinate were added at 70.degree. The dispersion was subsequently filtered. The pH value of the 50% dispersion was 2.0 and the average particle size was about 190 nm. Sulfur content of dried polymer: 1.0% 2. Methyl methacrylate-n-butyl methacrylate 90/10-copolymer A1, but 2700 g of methyl methacrylate and 300 g of butyl methacrylate
was used for injection. The pH value of the 50% dispersion is 2.0
The average particle size was approximately 240 nm. Sulfur content of the dried polymer: 1.02% Obtaining the solid: Obtaining the solid from the dispersion was carried out by spray drying. The reduced viscosity ηspez/c, measured in chloroform as solvent, is: Polymer A1: 8 ml/g and Polymer A2: 8.5 ml/g and the corresponding Mw (weight average) values: Mw (weight average) = 5870g/mol and M
w (weight average) = 5930 g/mol.

B. Processing of PVC-ABS mixtures by injection molding Polymer component P as commercial product for preparation for mechanical processing
VC and ABS were mixed together with commercially available PVC additives such as pigments, lubricants and stabilizers as well as low molecular weight polymethacrylates according to the invention. The mixture thus obtained (Dry Blend) can be further processed as such directly on the injection molding machine or can even be granulated before injection molding.

Table 1 lists the formulations obtained with such mixtures in the case of high-pressure-capillary-viscosity measurements (see flow properties) and in the case of injection molding (helical flow). The compositions and results are described, except for the following for comparison from processing with additive-free mixtures according to the invention: Tests 1, 6 and 11.

[0029]

[Table 1]

Claims (6)

[Claims] Claim 1. In a machining process for converting PVC-containing incompatible polymer mixtures into plastic compound products, the polymer mixture has a g content in the range from 2000 to 20000 g
Machining process for converting PVC-containing incompatible polymer mixtures into plastic compound products, characterized in that an alkyl methacrylate copolymer having a molecular weight Mw (weight average) of /mol is added. 2. The polymer mixture has a ratio of 70:30 to 30:
PVC- containing PVC and ABS in a weight ratio of 70
2. The process as claimed in claim 1, wherein the PVC-ABS mixture is an ABS mixture and the alkyl methacrylate copolymer is added in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the polymer mixture. 3. The process as claimed in claim 1, wherein the alkyl methacrylate copolymer is composed of 50 to 100% by weight of methacrylic acid alkyl esters having 1 to 8 C atoms in the alkyl group as monomers. 4. The alkyl methacrylate copolymer contains 50 to 98 methyl methacrylate as a monomer.
4. A method according to any one of claims 1 to 3, consisting of % by weight. 5. The alkyl methacrylate copolymer contains methyl methacrylate 60-95 as a monomer.
wt% and n-butyl methacrylate 40-5 wt%
5. A method according to any one of claims 1 to 4, comprising: 6. The alkyl methacrylate-copolymer contains at least 5 methyl methacrylates as monomers.
0% by weight, 2-50% by weight of alkyl methacrylates with 2-8 C atoms in the alkyl group, 0-48% by weight of alkyl acrylates with 1-8 C atoms in the alkyl group and optionally is another monomer 0
5. A method according to any one of claims 1 to 4, consisting of ~48% by weight.